If someone we care about is in harm’s way, most of us would do anything to protect that person, even if it means hurting an outside party. Now, a new study by researchers from the University at Buffalo, NY, sheds light on why warm feelings for one person can lead to anger toward another.

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Researchers find that a feeling of compassion for one person may lead to aggression toward another – a process that may be explained by the hormones oxytocin and vasopressin.

That compassion can lead to anger certainly seems illogical. But study authors Michael J. Poulin and Annette E. K. Buffone – both of the Department of Psychology at the University at Buffalo – believe it is down to the actions of two hormones: oxytocin and vasopressin.

The team explains how they reached these findings in their two-part study, published in the journal Personality and Social Psychology Bulletin.

The first part of their research required participants to complete a survey, which asked them to provide information about a person they are close to and to report a time when this person was threatened by a third party. Participants were then asked to describe their own emotions when this person was threatened and how they reacted to the situation.

The second part of the study involved an experiment. Firstly, participants were asked to provide a saliva sample, from which the researchers could measure their hormone levels.

The participants were then told a story about an individual they had never met and were informed that this individual was in a nearby room with another stranger. The story that participants were told was designed to evoke compassion for the unknown individual.

Participants were then informed that both of these people in the nearby room would be taking a math test and would be exposed to painful stimulus (in the form of hot sauce) to determine how physical pain affects their performance.

Subjects were told they could choose how much pain was inflicted on the stranger who was competing against the individual they felt compassion for.

According to Poulin, the overall results reveal that “the feelings we broadly call empathic concern, or compassion, can predict aggression on behalf of those in need,” adding:

In situations where we care about someone very much, as humans, we were motivated to benefit them, but if there is someone else in the way, we may do things to harm that third party.”

The researchers point out that this reaction may not be a result of a third party doing something wrong. Poulin uses the example of parents of a child taking part in a competition; the parents may do something destructive toward another participant so that their child wins the competition.

The team found that this response may be explained by variations on genes for both oxytocin and vasopressin receptors.

In the experiment, for example, participants who had compassion for the unknown individual in combination with an oxytocin gene receptor variation felt the need to put the third party through more pain. This result was also evident in participants who empathized with the unknown individual’s distress and had variation in the vasopressin receptor gene.

The researchers say that this finding makes sense. “Both oxytocin and vasopressin seem to serve a function leading to increased ‘approach behaviors,'” explains Poulin.

Oxytocin is often referred to as the “love hormone,” as it increases human bonding, while vasopressin has been linked to sexual motivation. As such, the team believes it is not surprising that these hormones may play a role in the association between compassion and aggression.

In April, Medical News Today reported on a study suggesting that oxytocin, despite encouraging bonding, may also cause us to lie in order to help those we care about.